Acceleration sensor apparatus and method for making same

ABSTRACT

An acceleration sensor is shown having a substrate (16, 16&#39;, 16&#34;, 16&#39;&#34;) on which a capacitor detect plate (24) and source plate mounting portion (28c) are disposed. An electrically conductive blade member (40, 44) having an attachment portion (40a, 44h), a source plate portion (40i, 44a) and integrally attached beams (40b, 40c; 44b) extending along opposite sides of the blade member is mounted on the substrate by welding the attachment portion to a mounting element (36, 36&#39;, 36&#34;, 36&#39;&#34;) which is closely received in a bore (32, 32&#39;, 32&#34;, 32&#39;&#34;) formed through the substrate at the source plate mounting portion. The mounting element or the bore is formed with a surface suitable for forming an interference fit and for making electrical engagement with a conductive layer received in the bore. The mounting element has one end (36b, 36b&#39;, 36b&#34;) which extends above the top surface (26, 26&#34;) an adjustable selected amount(s) to provide desired spacing between the source plate portion and the detect plate. A single mounting element of a pair of mounting elements can be used and may be in the form of a solid (36, 36&#34;, 36&#39;&#34;) or a hollow (36&#39;) pin.

BACKGROUND OF THE INVENTION

This invention relates generally to condition sensors and moreparticularly to accelerometers having mechanically movable meansresponsive to acceleration for providing a corresponding electricalsignal.

Condition sensors such as capacitive accelerometers and the like ofvarious types as shown in U.S. Pat. Nos. 4,483,194 to Rudolph; 4,435,737to Colton; 31,549 to Block and 3,240,073 to Pitzer are commonly used orproposed for use in aircraft and vehicular applications and the likewhere the sensors are likely to be subjected to shock, vibration andsevere temperature changes but where it would be desirable for thesensors to be inexpensive and to display reliable and accurateperformance characteristics over a long service life. However, many suchsensors have limited performance capability or are manufactured atexcessive cost. It would be desirable if such sensors could be providedwith improved reliability in performance and could be made at reducedcost to find wider application.

In application, Ser. No. 07/790,956, now U.S. Pat. No. 5,345,823assigned to the assignee of the present invention, compact, rugged andinexpensive accelerometer devices are disclosed comprising a stiff,rigid, electrically insulating ceramic substrate having a recess in theform of a groove formed in one substrate surface. Electricallyconductive film means are deposited on that surface to define acapacitor detect plate inside the recess, a capacitor source plateconnector pad outside the recess and circuit paths which are connectedto the detect plate and source plate connector and to respectiveterminal pads along an edge of the substrate surface. The accelerometerdevice further includes a flat, electrically conductive plate or blademember of stiffly resilient metal which is formed with an attachmentportion, a capacitor source plate portion and integral resilient beammeans in a common plane. The attachment portion of the member is securedin electrically conductive relation to the source plate connector on thesubstrate with a thin layer of solder. Spacing between the uppersurfaces of the detect plate and the source plate is determined by thedepth of the recess. In one embodiment, glass frit including a bondingglass meltable at one temperature and glass rods of a small, preciselydetermined diameter which remain shape-retaining at the meltingtemperature of the bonding glass is deposited over two spaced portionsof the source connector to provide a precise level of attachment of thesource plate to the source plate connector.

Although devices made in accordance with the teachings of the abovereferenced patent application are very effective and perform well, theuse of solder as a means of attachment involves a relatively timeconsuming reflow process and requires flux cleansing. In addition, thereis a tendency for elements connected by solder to move slightly overtime due to so-called solder creep thereby adversely affectingcalibration of the device.

In application, Ser. No. 07/628,249, now U.S. Pat. No. 5,239,871assigned to the assignee of the present invention, another accelerometerdevice is shown comprising an essentially flat electrically insulatingsubstrate with a detect plate and a source plate connector disposedthereon and with a similar conductive blade member secured to thesubstrate in electrically conductive relation to the capacitor sourceplate connector. Spacing between the source plate portion and thedetector plate is accomplished by using a shim between the attachmentplate portion and the source plate connector in one embodiment and inanother embodiment by reducing the thickness of the metal plate.However, use of a shim adds an additional part and process step whichadds to the cost of the device as well. Further, when using a shim it isdifficult to obtain close dimensional control from device to device. Useof a metal plate having a reduced thickness portion results in a moreexpensive blade member and one for which it is difficult to provide aproperly balanced and mounted source plate portion.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved accelerationsensor; to provide a novel and improved acceleration sensor which isparticularly adapted for use in vehicle applications; to provide animproved movable blade and an improved method for attaching the movableblade to the acceleration sensor and structure provided by such method;to provide an accelerometer device having lower thermal errors thanprior art accelerometer devices; and to provide an acceleration sensorwhich is of compact, rugged structure yet relatively inexpensive toproduce.

Briefly, in accordance with the invention, a base having at least thetop surface of electrically insulating material is provided with anelectrically conductive detect plate on a top surface thereof and atleast one bore between top and bottom surfaces. An electricallyconductive metal plate or blade is formed having an attachment portion,a source plate portion and an integral beam means connecting theattachment portion to the source plate portion. The attachment portionis fixedly attached, as by welding, to the end of an electricallyconductive element such as a solid or hollow pin inserted into the borewith the source plate portion spaced a selected distance from the detectplate and with the element in electrical engagement with a conductivepath which extends from the top surface of the substrate into the bore.According to a feature of the invention, once the metal blade is fixedto the pin, the axial position of the pin may be adjusted to provide aselected capacitance level between the detect plate and the source plateportion. According to another feature of the invention, the conductivepath is formed by screen printing on the top surface and drawing theliquid coating material by means of a vacuum through an annular spacedefined between the wall of the bore and an insert placed in the boreduring the coating step. The bore is specially formed with a flowinducing entrance, a burr accommodation section and a flow preventingexit. In accordance with one embodiment, the pin is knurled along atleast a portion of its length while in another embodiment the pin isformed with a plurality of longitudinally extending ribs having an outersurface forming arcs of a circle having a diameter which provides aninterference fit in the bore. In another embodiment the pin is tubularwith a closed end formed into a weld projection surface. In yet anotherembodiment the bore is formed with a plurality of splines or otherinwardly projecting surface portions and the pin is formed with aconventional cylindrical wall surface. The pin is inserted into the borewith an insertion force of between approximately 10 pounds minimum and200 pounds maximum. According to another embodiment, a pair of bores areprovided in the base and a pair of pins are attached to the attachmentportion and inserted in respective bores to prevent any possiblerotational movement of the pins. According to a feature of theinvention, the pin(s) and conductive metal plate may both be formed ofthe same material, for example, alloy 42 when the substrate is formed ofAl₂ O₃ ceramic to closely match the thermal coefficient of expansion ofthe substrate. In one embodiment of the invention the attachment portionof the metal blade member is disposed at one end portion of the bladewhile in another embodiment the attachment portion is disposed in thecenter of the blade member to provide a center of mass of the blademember in alignment with the location of attachment. An additionaladvantage of a central attachment portion is that it provides a shorterdistance between the location of attachment and the center of seismicmass.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, advantages and details of the novel and improvedaccelerometer sensor of the invention and of the method of making thesensor appear in the following detailed description of preferredembodiments of the invention, the detailed description referring to thedrawings in which:

FIG. 1 is a plan view of an acceleration sensor made in accordance withthe invention;

FIG. 2 is a plan view of a base member used in the sensor of FIG. 1;

FIG. 3 is a side elevation view, partially in section, of the sensorshown in FIG. 1;

FIG. 4 is a plan view of a substrate shown in a larger scale used in afirst embodiment of the invention;

FIG. 5 is an enlarged cross sectional view taken on line 5--5 of FIG. 4;

FIG. 5a is an enlarged cross sectional view taken through a portion of asubstrate shown with a screen printing fixture received in a bore in thesubstrate;

FIG. 5b is a bottom plan view of the FIG. 5a substrate and fixture;

FIG. 6 is a plan view of an enlarged scale of a blade member used withthe FIG. 4 substrate to form a sensor adapted to be received in the FIG.2 base member;

FIG. 7 is a cross sectional view of an enlarged scale of a portion of asubstrate and a blade member in a jig in preparation for attachment ofthe blade member to a support provided in a modified embodiment of theinvention;

FIG. 7a is an enlarged cross sectional view of a portion of a blademember attachment element used in the FIG. 7 embodiment;

FIG. 8 is a plan view of reduced scale of the FIG. 4 substrate with theFIG. 6 blade member mounted thereon;

FIG. 9 is a plan view of the same scale as FIG. 8 of a modifiedsubstrate useful with the FIG. 6 blade member;

FIG. 10 is a plan view of an enlarged scale of a modified blade memberuseful in the FIG. 1 acceleration sensor;

FIGS. 11 and 12 are front elevation and top views, respectively, of anenlarged scale of a blade member mounting element used in anotherembodiment of the invention;

FIGS. 13 and 14 are a plan view and a front view, respectively, of asubstrate adapted for use with the FIG. 10 blade member;

FIG. 15 is an enlarged cross sectional view taken on line 15--15 of FIG.14;

FIG. 16 is a plan view of the FIG. 13 substrate with the FIG. 10 blademember mounted thereon;

FIG. 17 is an enlarged cross sectional view similar to FIG. 15 but withthe FIG. 10 blade member mounted on the FIG. 11 pin; and

FIG. 18 is a plan view of a portion of a substrate having a splined boresuitable for receiving a standard cylindrical blade member attachmentelement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1-3 of the drawings an acceleration sensor 10 made inaccordance with the invention, includes a housing 12 having suitablemounting tabs 14 for attachment to a body, such as a vehicle, theacceleration of which is desired to be monitored. A substrate 16, FIG.4, formed of suitable material such as electrically insulative aluminumoxide, Al₂ O₃, is provided with slots 18 adapted to receive mountingposts 20 in a recess 22 of base 12. It will be understood that thesubstrate could be composed of various materials such as metal, forexample, having an electrically insulative top surface, if desired.Substrate 16 is provided with an electrically conductive detect plate 24on a top surface 26 thereof. Plate 24 can be placed on the substrate inany suitable manner, as by screen printing. Associated circuit paths28a, 28b, 28c are also formed on surface 26 in a similar manner. A bore32 is formed extending through the substrate 16 at source plate mountingportion 28c and is provided with a shallow recess 32a (FIG. 5) on topsurface 26 and a relatively larger well recess 32b on bottom side 34surrounding bore 32. A mounting element in the form of a pin 36, formedof material having a coefficient of thermal expansion closely matchingthat of substrate 16, is received in bore 32. For example, where thesubstrate employed is composed of 94 percent alumina ceramic, pin 36 canbe formed of Alloy 42, an alloy having a nominal composition by weightof 42 percent nickel and the balance iron. Both Alloy 42 and 94 percentalumina have coefficients of thermal expansion approximately 6.0×10⁻⁶cm/cm/°C. in the temperature range from 25° to 100° C. and comparableexpansion properties over the range -40° C. to 125° C. Pin 36 is formedwith a knurled surface portion 36a which extends around its peripheryfor a selected longitudinal portion of its length to provide aninterference fit in bore 32. For a bore in the order of 0.094/0.096inches the diameter of pin 36 can be on the order of 0.099/0.097 inchesso that a force of between approximately 10 and 200 pounds is requiredfor inserting the pin into the bore without cracking the substrate. Pin36 is formed with a curved end portion 36b on either end to serve as aweld projection.

Preferably, at least circuit path 28c is formed of metallo-organic goldin order to provide a sub-micron surface conductive path on the walldefining bore 32 which will not be wiped off by pin 36 when it isinserted in bore 32. Preferably, recess 32a is formed in top surface 26to form a flow inducing surface. As seen in FIG. 5a, a frusto-conicalramp having a shallow angle, for example, 13° relative to surface 26 hasbeen found to be suitable for promoting flow of coating material intothe bore. Ramp 32a blends in with a radius 33 of approximately 0.025inches at approximately 0.002 inches below top surface 26 formed at theentrance of burr accommodation section 33a. This provides adequatematerial above the radius so that grinding of the top surface to providea smooth flat surface will not affect the radius and there will be asmooth, gradual curved surface on which the liquid coating material canflow during the screening process. Intermediate burr accommodationsection 33a preferably is used to provide sufficient space and a trapfor any burr which might occur when a mounting pin is inserted into bore32 from surface 26 thereby preventing any interference fit with thewelding operation or the blade. A transition surface 33b extends fromsection 33a to bore 32 and is inclined relative to the longitudinal axisof bore 32 at a suitable angle, e.g., 35°-45°, to ensure that coatingmaterial applied to the bore will not be interrupted. On the other handwell recess 32b is formed on the bottom surface 34 with a surfaceportion 32c which is preferably 90° or more relative to the walldefining bore 32 so that the flow of any coating material received inthe bottom of the bore will be interrupted to break the conductive pathand prevent any possibility of an electrical shorting path to bottomsurface 34. Well 32b can also conveniently receive epoxy which can beprovided if desired, as an additional locking mechanism for the pin oncethe device has been calibrated as will be discussed infra. As seen inFIG. 5a a screen printing fixture pin 32d is preferably used when screenprinting the conductive layers onto substrate 16. Pin 32d has an outerdistal post portion 32e having an outer diameter selected to be slightlysmaller than the diameter of bore 32 in order to define an annularopening between the pin and the wall defining bore 32 so that thecoating material will flow through the annular opening in intimatecontact with the wall to ensure that the entire wall surface is coated.Portion 32f of pin 32d closely fits within bore 32 and centers post 32ewithin the bore while bores 32g provide channels for applying a suitablevacuum indicated by arrow 32i to draw the coating material down into thebore. With a bore 0.099-0.097 inch a distal post portion 32e having adiameter of approximately 0.082-0.088 inch provides a suitable annularpassage between the substrate and the distal post portion 32e ofapproximately 0.005-0.009 inch for use with metallo-organic gold.

After the coating operation has been completed insertion of pin 36 intobore 32 using an interference fit results in the knurled surface 36aelectrically engaging material 28c on the wall defining bore 32.

An electrically conductive blade member 40, FIG. 6, of the typedisclosed in copending application, Ser. No. 07/790,956 referencedsupra, which may be formed of the same material as pin 36, e.g., Alloy42, has an attachment portion 40a which is attached to pin 36 as byresistance welding or the like on weld projection 36b. Blade member 40has integrally attached first and second beams 40b, 40c extending awayfrom attachment portion 40a on opposite sides of blade 40 to arespective distal end 40d, 40e. Third and fourth beams 40f, 40g extendlaterally from the distal ends to a central portion 40h attached tosource plate portion 40i which extends back toward attachment portion40a. Attachment portion 40a is welded to pin 36 so that source plateportion 40i is aligned over detect plate 24 as shown in FIG. 8. Weldingcan be effected either before or after the pin is inserted into bore 32.Once inserted, electrical continuity can be checked between pin 36 andoutput pad 28d. If the pin is welded to the blade member prior toinsertion into bore 32 capacitance between the detect plate and thesource plate portion can be monitored by connecting them to anelectrical source as denoted by arrows T1 and T2 in FIG. 4. A force isthen applied through the blade member to the pin pushing the pin intothe bore until a selected capacitance value is obtained. If the pin isinserted into the bore prior to welding, this can be convenientlyaccomplished by inserting the pin into the bore leaving a space betweenthe top of the pin and a plane in which the detect plate lies, i.e., thetop surface of the substrate, greater than that which will provide theselected capacitance level, e.g., greater than "s" shown in FIG. 15, andthen welding the blade member to the pin. The capacitance is thenmonitored as a force is applied through the blade member to the pinmoving the pin until the selected capacitance level is obtained. It willbe realized that the pin could also be inserted, prior to welding,leaving less than the space required to provide the selected capacitancelevel and then a force could be applied to the bottom of the pin throughbore 32 pushing the pin and blade member away from the detect plateuntil the selected capacitance value is obtained. In all of the aboveprocedures the position of the pin can be adjusted to provide the gaprequired to obtain the selected capacitance level resulting in virtually100 percent yield and providing consistency from one device to another.This provides additional advantages in enhancing the frequency responseor damping factor due to the consistent air gap from device to device aswell as facilitating placement of stop surfaces to prevent over-travel.

A modified embodiment is shown in FIG. 7 in which the blade membermounting element takes the form of a cup-shaped hollow pin 36' in placeof the solid pin 36 shown in FIG. 5. Hollow pin 36', again, may beformed of the same material as blade 40, e.g., 0.010 inch Alloy 42, andis inserted into bore 32 in substrate 16. Blade member 40 is placed in arecess 42a of a suitable electrically insulating jig 42. A movableelectrode 42b is received in hollow pin 36' and a stationary electrode42c is disposed in a bore 42d of jig 42 and in alignment with electrode42b for welding hollow pin 36' to blade 40. Preferably, hollow pin 36'is formed with a radiused closed end 36b', as shown in FIG. 7a to serveas a weld projection.

Another modified embodiment of the invention is shown in FIG. 9 in whichsubstrate 16' is provided with a pair of bores 32' in order to provideimproved anti-rotational control of a blade member mounted on thesubstrate.

FIG. 10 shows a preferred embodiment of a blade member having anintegral source plate portion with improved thermal errorcharacteristics. Any differences in coefficient of thermal expansion ofjoined ports, however small, will result in the joint being stressedwhen changes in temperature of joined materials occurs. The most commoneffect of this thermal stress is a bending of the joinedmaterial--called the bimetal affect. Blade member 44 incorporatesseveral features which minimize the outward affects of bending caused bythermal expansion mismatch in the attached joint.

As in the previous embodiments, blade member 44, is formed of materialhaving a selected coefficient of thermal expansion relative to that ofthe substrate to which it is to be mounted. Blade member 44 has a sourceplate portion 44a, the center of seismic mass, attached at each lateralside to a respective beam 44b defined by a slot 44c which extends thefull length of blade member 44, i.e., along a y-axis. Each opposite endof beam 44b is integrally attached to a respective side of a centralbrace portion 44b. Central brace portion 44d is attached at each side toa laterally extending, i.e., along an x-axis, slender isolation beam 44edefined by a laterally extending slot 44f and a curved end portion 44gof slot 44c. Beams 44e are in turn connected to an attachment portion44h through slender, laterally extending isolation beams 44i and acounterflexing zone 44j. Beams 44i extend above and below isolationwindows 44k and are defined by slot 44l on the top and slot 44f on thebottom, as seen in FIG. 10. Isolation slots 44m extend downwardly fromslot 44l to match end portions 44n of slot 44f.

A welded attachment to a mounting member is made at attachment portion44h. Changes in temperature will result in a bending stress beingapplied to the weld region causing the blade member to bend or develop acurvature. The input to the blade member from this curvature is toimpose a curved boundary condition to the blade member at the attachmentarea. The boundary condition is circular in nature and will causebending around the x-axis and the y-axis. Windows 44k cut in theattachment portion create two slender, laterally extending isolationbeams 44i that reduce the rigidity of the attachment portion. Along thex-axis the beams bend to form an "s" shape in the direction of thez-axis, i.e., perpendicular to the plane in which the blade member lies,which reduces the transmission of stress boundary condition rather thanacting as a stiff lever arm as would happen without windows 44k. Beammembers 44i also twist in response to the y-direction imposed boundarycondition. Isolation cuts 44m, 44n enhance the ability of beam members44i to twist. The counterflexing zone 44i extends from the isolationcuts 44m down to the curved slot 44g. The function of the counterflexingzone is to contain remaining x-direction bending stresses to thex-direction. The lateral position of curve slot 44g relative to slot 44fis selected to define slender beams 44e which extend laterally,generally parallel to beam 44i to central brace portion 44d. If curvedslot 44g were moved outward toward beams 44b, a y-direction stresscomponent would be generated, forcing central brace portion 44d to tilt,changing the capacitor gap at source plate portion 44a. The centralbrace portion 44d is a stiff section to stop further transmission of theboundary condition stress. The end result of this arrangement of beamsand holes is to allow thermal stresses generated in the weld attachmentto gradually be diminished, while not changing the capacitor gap atsource plate portion 44a.

The critical aspects of blade member 44 to enable good drop performanceare those that minimize stress concentrations during a cross axis shockwhile allowing a high degree of flexibility in the sensing direction.Curved slot feature 44g is formed with a relatively large radius toreduce notch stresses from an x-axis drop. Tapered sections 44o and 44pof beams 44b are tapered to minimize the moment stress applied to thearcs where beams 44b are connected to central brace portion 44d. Thewidth of slot 44c is selected to allow counterflexing zone 44j to act asa cross axis stop. This minimizes stresses generated in beams 44b. Thewelded attachment area is positioned over the center of mass of theblade member to minimize torsional shear stress of the weld during across axis shock test.

The size of source plate portion 44i is selected for controlling thesqueeze film damping factor. That is, if the size is too small, portion44i will resonate and if it is too large, it will not be sufficientlysensitive. Beams 44b are sized to provide adequate movement of theseismic mass, i.e., portion 44i. The blade is chemically etched usingstandard integrated circuit lead frame processing to provide a stressfree, flat part preferably in reel form. Mounting parts on reels reduceshandling and transportation damages as well as allows for high speedautomated assembly.

With respect to FIGS. 11 and 12 a pin 36" is shown formed with aplurality of longitudinally extending ribs 36a", preferably having aradiused outer peripheral surface. The ribs can be formed by anysuitable means as by stamping equally spaced flat portions 36d" eachcovering 90°, for example, leaving three ribs each covering 30° andhaving an outer radius for each rib comparable but slightly larger thanthat of the pin before stamping. For use with a bore 0.099/0.097 inch indiameter, pin 36" is acceptable if it passes through a ring gap of0.1015 inch and not pass a gap of 0.1005 inch. As mentioned above,acceptable insertion force can be anywhere from approximately 10 toapproximately 200 pounds. More specifically, with regard to the FIGS. 11and 12 pin, an insertion force of between 50 and 100 pounds has beenfound to be suitable. Ends 36b" of pin 36" are formed with a suitableradius such as 0.125/0.280 to serve as a weld projection so that eitherend can be inserted in the bore.

Substrate 16" shown in FIGS. 13-15 may be composed of the same materialas substrate 16 discussed supra, e.g., 94 percent alumina. Bore 32" iscentrally disposed on top surface 26" and pin 36" may be forced intobore 32" so that weld projection surface 36b" extends above the surfacea selected distance "s" shown in FIG. 15. Blade member 44 is mounted onsubstrate 16" by welding attachment portion 44a to weld projectionsurface 36b" with source plate portion 44i aligned with and spaced overdetect plate 24. In order to ensure the desired spacing, spacers ofKapton, or the like can be placed between blade member 44 and surface26" on opposite sides of attachment portion 44a or specially machinedfixtures can be employed. However, preferably, as described above withreference to blade member 40, blade member 44 may be welded to pin 36"before or after being inserted into bore 32" and the capacitance betweensource plate portion 44a and detect plate 24 can be monitored as the pinis moved in the bore with movement being stopped at the appropriatespacing when the selected capacitance value is obtained.

It is also within the purview of the invention to use a pin 36'" havinga smooth cylindrical surface and to form bore 32 with a plurality ofsplines 32a are spaced about the periphery and projecting into the boreso that an interference fit is formed between pin 36'" and splines 32aas shown in FIG. 18.

Though the invention has been described with respect to specificpreferred embodiments thereof, many variations and modifications willimmediately become apparent to those skilled in the art. It is thereforethe intention that the appended claims be interpreted as broadly aspossible in view of the prior art to include all such variations andmodifications.

What is claimed:
 1. An acceleration sensor comprising a substrate havingopposite top and bottom surfaces, at least the top surface beingelectrically insulative, an electrically conductive detect plate mountedon the top surface of the substrate, a bore extending through thesubstrate between the top and bottom surfaces of a preselected diameter,an electrically conductive mounting element disposed in the bore andhaving an end extending above the top surface by a selected distance,said mounting element having an outer surface portion which engages saidbore of preselected diameter and requires a force of between 10 and 200pounds to insert the mounting element into the bore for precisely andfixedly holding the mounting element in place after insertion whilestill allowing for movement and adjustments of the mounting element forcalibration after insertion, an electrically conductive metal blademember having an attachment portion, a source plate portion andintegral, resilient beam means extending between the attachment portionand the source plate portion, the attachment portion fixedly andelectrically attached to the end of the mounting element extending abovethe top surface, electrically conductive circuit paths electricallyconnected with the detect plate and the mounting element, the sourceplate portion overlying the detect plate in selected spaced relation toform a capacitor and to be movable relative to the detect plate inresponse to an acceleration force to provide an electrical signal.
 2. Anacceleration sensor according to claim 1 in which the attachment portionis attached to the end of the mounting element by being welded thereto.3. An acceleration sensor according to claim 1 in which the attachmentportion of the metal blade member is centralized relative to the plate.4. An acceleration sensor according to claim 1 in which a second bore isformed in the substrate between the top and bottom surfaces and a secondelectrically conductive mounting element is disposed in the second bore,the second mounting element having an end extending above the topsurface and being fixedly attached to the attachment portion of themetal blade member.
 5. An acceleration sensor according to claim 1 inwhich the substrate is formed of 94 percent alumina ceramic and themounting element and the metal blade member are each composed of metalhaving a nominal composition of 42% nickel and the remainder iron.
 6. Anacceleration sensor according to claim 1 in which the mounting elementis a hollow pin having a closed end forming the said end extending abovethe top surface.
 7. An acceleration sensor according to claim 1 in whichthe mounting element is a solid pin having a knurled outer surfaceportion.
 8. An acceleration sensor according to claim 1 in which themounting element is a solid, generally cylindrical pin having alongitudinal axis and having a plurality of longitudinally extendingribs formed on the pin.
 9. An acceleration sensor according to claim 1in which the bore is formed with a plurality of spaced projectionsextending into the bore and extending in a direction generally parallelto the longitudinal axis of the bore and the mounting element has agenerally cylindrical peripheral surface.
 10. An acceleration sensoraccording to claim 1 in which the mounting element is a solid, generallycylindrical pin having a longitudinal axis and having three spaced,longitudinally extending ribs formed on the pin, the outer surface ofthe ribs being curved and covering in total approximately 90° around theouter peripheral surface of the pin.
 11. An acceleration sensorcomprising a substrate having a top surface, an electrically conductivedetect plate mounted on the top surface of the substrate, anelectrically conductive metal blade member having an attachment portioncentralized relative to the blade member, a source plate portion andintegral resilient beam means extending between the attachment andsource plate portions, the beam means comprising first and secondisolation beams extending outwardly laterally from the attachmentportion toward opposite sides of the blade member and throughcounterflexing zones to a central brace portion at the first end of theblade member and a pair of beams extending from the central braceportion at the first end of the blade member toward a second end of theblade member opposite the first end and being attached to the sourceplate portion at the second end of the blade member, the source plateportion extending back toward the attachment portion, the attachmentportion being mounted on the substrate with the source plate portionoverlying the detect plate in selected spaced relation, circuit paths onthe substrate electrically connected to the detect plate and the metalplate to form a capacitor, the source plate portion being movablerelative to the detect plate in response to an acceleration force toprovide an electrical signal.
 12. An acceleration sensor according toclaim 11 further including third and fourth isolation beams extendinglaterally inwardly from respective counterflexing zones to the centralbrace portion, the third and fourth isolation beams extending in adirection generally parallel to the direction in which the first andsecond isolation beams extend.
 13. An acceleration sensor according toclaim 11 in which the substrate is formed with a bore extending throughthe top surface and an electrically conductive mounting element havingopposite ends is disposed in the bore with one end extending above thetop surface a selected distance and the attachment portion of the metalblade member is welded to the one end extending above the top surface.14. The method according to claim 13 where the annular space between thewall of the bore and the substrate is on the order of 0.005 to 0.009inch.
 15. An electrically conductive metal blade member for use with anacceleration sensor comprising an attachment portion centralizedrelative to the blade member, a source plate portion and integralresilient beam means extending between the attachment and source plateportions, the beam means comprising isolation beams extending from theattachment portion toward opposite sides of the blade member and throughrespective counterflexing zones to a central brace portion disposed atthe first end of the blade member and a pair of beams extending parallelto a y-axis from the central brace portion at the first end of the blademember toward a second end of the blade member opposite the first endand being attached to the source plate at the second end of the blademember, the source plate portion extending back toward and being closelyadjacent to the attachment portion.
 16. An electrically conductive metalblade member according to claim 15 in which the isolation beams includefirst and second pairs of beams extending laterally outwardly parallelto an x-axis from the attachment portion and further including third andfourth isolation beams extending laterally inwardly parallel to thex-axis from respective counterflexing zones to the central braceportion.
 17. An electrically conductive metal blade member according toclaim 15 in which a window is cut out between each pair of first andsecond isolation beams.
 18. An electrically conductive metal blademember according to claim 15 in which each beam of the pair of beamsextending parallel to the y-axis has a relatively narrow central portionand tapered, wider end portions.
 19. An acceleration sensor comprising asubstrate having opposite top and bottom surfaces, at least the topsurface being electrically insulative, an electrically conductive detectplate mounted on the top surface of the substrate, a bore extendingthrough the substrate between the top and bottom surfaces, with a recessformed in the top surface of the substrate in communication with thebore, the recess having a surface which forms an angle of approximately13 degrees or less with said top surface, an electrically conductivemounting element disposed in the bore and having an end extending abovethe top surface by a selected distance, an electrically conductive metalblade member having an attachment portion, a source plate portion andintegral, resilient beam means extending between the attachment portionand the source plate portion, the attachment portion fixedly andelectrically attached to the end of the mounting element extending abovethe top surface, electrically conductive circuit paths electricallyconnected with the detect place and the mounting element, saidelectrically conductive material extending from the circuit paths intothe recess and into the bore, the source plate portion overlying thedetect plate in selected spaced relation to form a capacitor and to bemovable relative to the detect place in response to an accelerationforce to provide an electrical signal.
 20. An acceleration sensoraccording to claim 19 in which a second recess is formed in a bottomsurface of the substrate in communication with the bore, the secondrecess being larger than the recess in the top surface to serve as awell for any excess conductive material and having a surface which formsan angle of approximately 90 degrees with a longitudinal axis of thebore.